Facile co-deposition of the carbon nanotube@MnO2 heterostructure for high-performance flexible supercapacitors

Herein, a facile co-deposition method is developed to synthesize carbon nanotube (CNT)@MnO2 heterostructures grown on carbon fibre paper (CFP) and flexible carbon fibre cloth (CFC) (denoted as CNT@MnO2/CFP and CNT@MnO2/CFC, respectively). A three-dimensional (3D) interconnected CNT network of highly conductive, ultrathin CNT@MnO2 heterostructure nanosheets with a nanoporous structure and with epitaxial growth of MnO2 on the CNTs achieves excellent capacitance performance for flexible MnO2-based supercapacitor materials. The CNT@MnO2/CFP fabricated in an electrolyte with CNT content of 0.5 g L−1 (0.5-CNT@MnO2/CFP) obtains mass, area and volume specific capacitance values of 393.0 F g−1, 585.0 mF cm−2 and 29.3 F cm−3, respectively, at a charge-discharge rate of 0.25 A g−1. A flexible asymmetric supercapacitor device was successfully assembled which possesses a high energy density of 27.8 Wh kg−1 at a high power density of 250 W kg−1 (0.75 mA cm−2) and a high capacitance retention of 84% after 10,000 performs at a charge-discharge rate of 15 mA cm−2 (5 A g−1). Our work confirmed that this structure can effectively improving the utilization and specific capacitance of MnO2, and the simplicity of the fabrication and the environmentally friendly characteristics of the deposition liquid make this approach suitable for practical production.